What's the point of running marathons?

See Runners for Life discussion forum for an interesting discussion on this topic. Most certainly if one is interested in health and fitness it is not necessary to run marathons. Its sufficient to run/walk 45 minutes a day 4-5 times a week. So why run marathons? According to the article Why run marathons because it's there, it's hard, yet an average person can do it. My personal view is that most of us amateur marathoners do it for the satisifaction of achieving a challenging goal and the high that comes with it, that is, the benefits are more internal than external. And once we achieve the goal of completing of our first full marathon many of us set ourselves even more challenging goals. This could be in terms of running faster marathons (and qualifying for Boston) or greater number of marathons (say 3 marathons in 3 months or 12 marathons in 12 months 0r 50 marathons in 50 states in 50 days ) or running extreme marathons(such as the Great Tibetan Marathon) or running beyond marathon distances : 50K, 100K or even 100 miles. None of these challenges are necessary for the health benefits but still lots of runners are doing this and the tribe is growing rapidly!!